The present invention relates to safety belts for vehicles transporting passengers in particular over ground, and more particularly relates to an improved mechanism for maintaining a strap of a safety belt in an adjustable position, this mechanism being adapted to be fixed to a structure.
As is known, for safety reasons, vehicles transporting passengers are usually provided with seats equipped with safety belts. This is for example the case of aircraft and automobile vehicles.
As concerns automobile vehicles travelling on the ground, safety belts are usually employed which have two or three anchoring points. When a safety belt having three anchoring points is used, the strap comprises a waist part and a chest part which crosses the chest of the wearer in the manner of a shoulder-strap.
When a safety belt of the last-mentioned type is used, the chest part occupies a position relative to the wearer which is a function of the morphology of the latter, of the geometry of the vehicle and seat and moreover of the state of fatigue of the wearer. Under these conditions, the chest part may be positioned in some cases at the level of the neck of the wearer. It will be understood that, in the event of a violent collision, with the safety belt immobilized under the control of an inertia detector, the body of the passenger is violently thrown forwardly and his neck encounters the strap which may then no longer act as a safety means but as a particularly dangerous object. Indeed, in some collisions, serious injury to the neck has been found, which is produced by the safety belt and more particularly the chest part thereof.
This is the reason why it has already been proposed to arrange that the upper anchoring point of the chest part be in an adjustable position in order to take into account the morphology of the wearer relative to the configuration of the vehicle.
Various devices have already been proposed.
Very often they are so arranged that the upper anchoring point of the chest part can occupy multiple positions within a range of positions which takes into account the extreme morphologies of a population relative to the mean morphology.
These devices, which are sometimes motorized, are very complicated. They very often employ mechanisms of the screw-and-nut type which therefore permits progressively varying the position of the upper anchoring point of the chest part of the strap of the safety belt.
Other embodiments employ catches and apertures with respect to which are movable carriages of anchoring mechanisms.
It will therefore be understood that all these devices are complicated and consequently not very reliable and relatively expensive.